Re: [PATCH 3.10 099/180] fix d_walk()/non-delayed __d_free() race
From: Ben Hutchings <hidden>
Date: 2016-08-27 11:39:13
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On Sat, 2016-08-27 at 11:31 +0200, Willy Tarreau wrote:
Greg, Jiri,
I checked Jari's explanation below and found that v3.14.77 and v3.12.62
are missing the same fix as 3.10. In fact Al's original commit 3d56c25
("fix d_walk()/non-delayed __d_free() race") used to mention to check
this __d_materialise_dentry() function in the Cc: stable line, but this
got lost during the backports.
Normally all of our 3 kernels need to apply the following patch that
Ben correctly put in 3.16 and 3.2. I'm fixing the backport in 3.10.103
right now.I never did get positive confirmation that this is the right change in __d_materialise_dentry(). Al, could you please comment? Ben.
quoted hunk ↗ jump to hunk
quoted
Cheers,Willydiff --git a/fs/dcache.c b/fs/dcache.c index 2a808fb..2d0b9d2 100644 --- a/fs/dcache.c +++ b/fs/dcache.c@@ -2401,6 +2401,7 @@ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)quoted
switch_names(dentry, anon); swap(dentry->d_name.hash, anon->d_name.hash);quoted
+ dentry->d_flags |= DCACHE_RCUACCESS; dentry->d_parent = dentry; list_del_init(&dentry->d_child); anon->d_parent = dparent;On Mon, Aug 22, 2016 at 04:56:57PM +0300, Jari Ruusu wrote:quoted
This patch for 3.10 branch appears to be missing one important + dentry->d_flags |= DCACHE_RCUACCESS; in fs/dcache.c __d_materialise_dentry() function. When Ben Hutchings backported Al Viro's original fix to stable branches that he maintains, he added that one additional line to both 3.2 and 3.16 branches. Please consider including that additional one line fix for 3.10 stable branch also. Ben Hutchings said this on his 3.2.82-rc1 patch: [bwh: Backported to 3.2: - Adjust context - Also set the flag in __d_materialise_dentry())] http://marc.info/?l=linux-kernel&m=147117565612275&w=2 Ben Hutchings said this on his 3.16.37-rc1 patch: [bwh: Backported to 3.16: - Adjust context - Also set the flag in __d_materialise_dentry())] http://marc.info/?l=linux-kernel&m=147117433412006&w=2 Also mentioned by Sasha Levin on 3.18 and 4.1 commits:quoted
quoted
Cc: stable@vger.kernel.org # v3.2+ (and watch out for __d_materialise_dentry())http://marc.info/?l=linux-stable-commits&m=146648034410827&w=2 http://marc.info/?l=linux-stable-commits&m=146647471009771&w=2 -- Jari Ruusu 4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD ACDF F073 3C80 8132 F189
-- Ben Hutchings [W]e found...that it wasn't as easy to get programs right as we had thought. ... I realized that a large part of my life from then on was going to be spent in finding mistakes in my own programs. - Maurice Wilkes, 1949
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